On Friday, TomKat jumped the couch. Katie Holmes filed for divorce from Tom Cruise after 5 1/2 years of marriage. Best-selling biographer Andrew Morton, author of “Tom Cruise: An Unauthorized Biography” (St. Martins Press), explains why it was a true Hollywood romance — because from the beginning, Holmes was playing a part.

He flew in singers, dancers and even Tom’s favorite sushi chefs for the bash, where the actor was serenaded with the medley of songs from his box-office hits.

“It’s the best birthday ever, ever, ever, ever, ever, and I mean ever,” he said, with typical understatement.

Tuesday, Tom’s 50th birthday, will lack some “evers.” He will be in his trailer in the wilds of Iceland, where he is filming the aptly named “Oblivion.” Instead of the expected cards and presents from Katie Holmes, she sent him a confetti of legal papers and correspondence marking the end of their five-year marriage.

At least one thing he knows he’ll get is a call from Miscavige, to congratulate and console. Wives may come and go. Scientology is forever.

Holmes’ bombshell, in the midst of his international publicity campaign for “Rock of Ages,” in which he stars as an aging singer, shows exquisite if cruel timing. Tom has admitted he was “blindsided” by her decision, just as Nicole Kidman, his second wife, was stunned when he abruptly decided to end their 10-year marriage even though she was pregnant.

As a leading member of a religion founded by science-fiction writer L. Ron Hubbard, Cruise doesn’t believe in karma. But Katie’s carefully executed escape plan means that, deliberately or not, she is getting one back for the sisterhood.

When he and Kidman divorced, Cruise effectively gained custody of their adopted children, Connor and Isabella. This time, however, Cruise has no such guarantees.

Holmes, presumably with the advice of her lawyer father, Martin Holmes, is playing hardball. She has hired a legal pit bull, New York lawyer Allan E. Mayefsky, who has been involved in several vicious splits, including the divorce of model Christie Brinkley. She wants full custody of Suri, the 6-year-old daughter Cruise dotes on.

Suri’s future education — whether in the rituals of Scientology, like her step-brother and -sister, or a more conventional avenue — will be a critical concern.

Suri is now at an age where she will face frequent formal interrogation about her behavior, what Scientologists call “sec checking.” In the fight for the heart and mind of Suri, her future religion — Katie was raised a Catholic — will be critical.

Like Nicole before her, Katie will now not just be Tom’s foe, but also considered an enemy of the Church of Scientology. When news leaked of the breakup, former high-ranking leaders of Scientology contacted me to say: “We told you so.” Since the beginning of the TomKat love fest, which began with the diminutive actor bouncing up and down on Oprah’s couch, they have known that the romance was as carefully choreographed by Scientology as his 42nd birthday party.

Even their prenup had, according to Scientology insiders, a series of mileposts where Katie would receive bonuses for how long she stayed with the actor. She received $3 million for every year of service, sources said — with a big bonus if she gave him children.

In the months before they married, they claimed Katie had signed up for a five-year contract. Well, those five years are now up — the couple married in November 2006.

For Katie to leave in this way — she made the announcement to a “saddened” Tom — shows how badly she wants out. Holmes saw what happened to her predecessor.

When the man dubbed “Tom Terrific” dumped Nicole Kidman in early 2001, she learned that she had been written out of the script of his life by his lawyer, rather than in a face-to-face conversation.

Kidman was toast the moment she said in an interview that she embraced a number of religions, not just Scientology. Given the fact that her father is a psychiatrist — deemed to be the mortal enemies of Scientology — she was already suspect. These public pronouncements put her beyond the pale. For the church’s most prominent poster boy, his partner had to be a Scientologist.

After Nicole, the search was on for a new partner for Tom Terrific. It didn’t take long. Sparks had already flown between the actor and his new leading lady, Penelope Cruz, during the making of “Vanilla Sky.” She was groomed as Kidman’s successor. He took the Spanish actress to Scientology’s Celebrity Centre in Hollywood and encouraged her to take a few courses.

While Penelope studiously read Scientology texts and attended auditing courses — the equivalent of a confessional — she was never really committed.

“I have great respect for all religions, but I do not intend to join any of them at the moment,” she said tactfully, but fatally for her chances of marrying the Scientologist leading man.

When their relationship officially ended in 2004, no one was happier than her father, Eduardo, who had secretly been in touch with an organization based in Germany — the most hostile European country to Scientology — which helps members of cults and their families.

After the Cruz breakup, the lovelorn actor turned to his best friend, Scientology leader Miscavige, for help in finding a new wife. The diminutive church boss, who has a notoriously volcanic temper, became irritated with constant calls from Tom. As the head of a multibillion-dollar operation, he felt it was below him to be seeking out women for the Hollywood star. He deputized his wife, Shelly, to take over the task.

The first girl she chose seemed ideal. She was a Sea Org member, that is to say committed to working full time for Scientology. The girl found herself “running into” Cruise, all the while thinking she was auditioning for a part in a movie. She dated Cruise a couple of times but then asked Scientology spokesman Tommy Davis, the son of actress Anne Archer, if she was being deliberately “set up.”

Her reward was to be told by Davis on Cruise’s behalf that the relationship was over. Then, according to friends, she was sent to a top security Scientology base and forced to scrub public bathroom floors with a toothbrush as punishment for messing up her assignment.

Tom had already moved on, briefly romancing 19-year-old actress Yolanda Pecoraro, whose only claim to fame was appearing as a bikini babe in the TV drama “Dr. Vegas.” She did, though, bear a remarkable resemblance to Penelope Cruz. The daughter of a Nicaraguan mother and Italian father, she had been a Scientologist since the age of 13 and was by the side of the actor when he received a special Scientology award in November 2004.

When that hookup bit the dust, he gave Scientology leaders a wish list of women he would like to date. They included Jennifer Garner and the up-and-coming actress Sofia Vergara.

When Vergara got an invitation from Cruise’s friend Will Smith to attend a pre-Oscar party, she had no idea she was being set up. She was dazzled by Tom’s megawatt smile and amused by the blizzard of phone calls, flowers and chocolates that followed their first meeting.

It was not long before he casually suggested they head for Celebrity Centre where, surprise, surprise, Miscavige was waiting to layer on the charm. It soon became clear that she was being auditioned for the biggest role of her life — Mrs. Tom Cruise Mark III. It was made clear that if she took the part, she would have to renounce her Catholic faith and convert to Scientology.

“She was fundamentally terrified of Scientology,” a friend told me. “She sincerely believed that she would be struck down by God and burn in hell if she joined.”

Exit Sofia — running for the hills.

After that debacle, the church went into overdrive to find him a partner. They put out a casting call for possible brides, telling them that there was an upcoming Cruise movie they might get a part in. Former Scientologist Marc Headley, who filmed many of the auditions, recalls that first they rounded up Scientology actresses like Erika Christensen, Erica Howard and Sofia Milos. None was deemed acceptable.

They were looking for a woman who would accept the teachings of Scientology, but who would also look good on Tom’s arm — and not make too many waves.

“They had to look outside the herd, so to speak. They went for Jennifer Garner, Scarlett Johansson and Jessica Alba, in that order. Jennifer and Jessica didn’t bite, but Scarlett took the bait and came in for an audition. When she arrived at the address and found out it was the Scientology center in Hollywood, she freaked out and didn’t do a tape.”

Finally, the Scientology casting crew hit on Katie Holmes, then 26, after they read an interview in which she said she would like to marry Tom. A senior Scientologist was sent to New York to give her the once-over. He liked what he saw.

She must have been thrilled. Ever since she was a little girl, she had told her three older sisters that she was going to marry Tom and live in a beautiful mansion where she would start the day by sliding from her bedroom into her own swimming pool.

Their first meeting was right out of the Cruise book of romance. He took her on a motorcycle ride to the beach at Santa Monica, later sending a limousine filled with chocolates and flowers to her apartment.

“I was in love from the moment I shook his hand,” she later gushed. In the coming months, the former star of “Dawson’s Creek” would turn gushing into an art form.

Tom, meanwhile, was bouncing up and down — literally. Vergara watched their antics from a distance, and thanked her lucky stars. “She had a narrow escape,” recalled a friend. “She privately pitied the poor girl. Katie is a much weaker, more innocent person than Sofia.”

It had been only six weeks since Katie had broken off her engagement with actor Chris Klein, and now she was falling into marriage with a star 17 years her senior. Her family and friends watched in horror as they saw the normally vivacious woman turn into a Stepford Wife, silent, dutiful and stooping. She was now nicknamed “Dead Eye” Holmes, the young actress cocooned by Scientology handlers wherever she went.

Katie may now regret signing in June 2005 a comprehensive contract with Scientology. But the reward was a proposal on top of the Eiffel Tower and marriage in an Italian castle in November 2006.

In her rare interviews since, her responses are brief, guarded and inconsequential, endlessly repeating the numbing mantra that her life is “magical.”

But, hey, presto, the magic has worn off. Hollywood’s modern-day Snow White has woken from her dream. While she and her family face whatever hocus-pocus Cruise and Scientology try on them, the search will be on for Mrs. Cruise Mark IV.